Disposable personal hygiene absorbent articles such as infant diapers or female sanity pads are mass-produced products. Modern processes allow the continuous production of these articles starting from the raw material (including pulp, superabsorbent polymers (SAP), nonwovens or films, elastic strings, etc.) to a finished bagged product ready for shipping on a single converting line. Complex article elements such as the absorbent cores can be pre-made at a supplier and then assembled to the other article elements at the converting line. In some processes, absorbent cores, especially for diapers, may be made in a core making apparatus directly feeding the converting line. The core making apparatus may lay down a mixture of cellulose pulp fibers and SAP to form the cores.
In some modern diaper converting processes, it may be possible to achieve a production speed in the order of 1000 diapers per minute. Modern converting lines are complex and very costly so that continuing development efforts are engaged to increase their production speed to maximize their production rate. However, in some processes, it has been difficult to increase the production speed over 1100 diapers per minute on a conventional manufacturing line because of processes limitations, in particular discrete transformations that cannot be made continuously such as intermittent gluing and application of discrete patches such as landing zones, ears, etc.
In some processes, absorbent cores may be oriented in cross-machine direction, assembled with certain article elements, and then turned in the machine direction for further converting on a single line. However, when the cores are turned in the machine direction, because the length to width ratio is usually of about 3:1, the downstream line speed needs to be accelerated to the same extent. This can create high mechanical forces during the turn and repitch operation that restraint the speed of the line achievable. In such design, line speed of 700 units per minutes is considered to be a maximum achievable.